A method for calculating magnetic field of an arbitrary shape energized coil considering magnetic shielding effect

Abstract

The application discloses a kind of arbitrary shape energized coil magnetic field calculation method considering magnetic shielding effect, it is related to the technical field of magnetic field calculation, by the technical method in the present application, in the physical scene of the existence magnetic shielding effect, arbitrary shape energized coil is equivalently converted into combination coil, then shielding coefficient considering magnetic shielding effect is added to each current-carrying straight segment, shielding coefficient is optimized by difference evolution algorithm, then the space magnetic field generated by energized coil at different positions is obtained by forward calculation;The magnetic field calculation method of the application can simplify the magnetic field calculation process of arbitrary shape energized coil under different application scenarios, improve the calculation efficiency, and has strong applicability and wide application range.

Description

Technical Field

[0001] This invention relates to the technical field of magnetic field calculation, and more specifically, to a method for calculating the magnetic field of an arbitrarily shaped energized coil that takes into account the magnetic shielding effect. Background Technology

[0002] A current-carrying coil generates a magnetic field in space. In some applications, this magnetic field is passively generated, such as in indoor cables primarily used for power transmission, but the resulting magnetic field can cause electromagnetic compatibility issues for surrounding equipment. In other applications, the magnetic field is actively generated, such as in ship degaussing systems where a degaussing coil generates a magnetic field to compensate for the ship's induced magnetic field against the background of the Earth's magnetic field. In these different applications, the current-carrying coils vary in shape, and the presence of ferromagnetic materials in the surrounding environment provides some shielding for the magnetic field, making the calculation of the coil's magnetic field extremely complex. Currently, there is no universal method for calculating the magnetic field of arbitrary-shaped current-carrying coils, and it is impossible to obtain the spatial magnetic field of a current-carrying coil under magnetic shielding effects through analytical calculation. Therefore, a universal method for calculating the magnetic field of arbitrary-shaped current-carrying coils that considers magnetic shielding effects is needed to simplify the calculation process and improve computational efficiency in different application scenarios. Summary of the Invention

[0003] The purpose of this invention is to propose a general method for calculating the magnetic field of an arbitrarily shaped energized coil that takes into account the magnetic shielding effect, so as to simplify the calculation process of the magnetic field of an energized coil in different application scenarios, improve the calculation efficiency, and the calculation method has strong applicability and wide application range.

[0004] The technical solution of this invention is: to provide a method for calculating the magnetic field of an arbitrarily shaped current-carrying coil considering the magnetic shielding effect, the method comprising the following steps:

[0005] S1. An arbitrarily shaped energized coil is equivalently divided into a combination coil of multiple straight segments. The straight segments of the coil are directly cut off at both ends to form straight segments. The arc segments of the coil are divided along the circumference and equivalently transformed into multiple straight segments. All the processed straight segments are combined to form an equivalent combination coil.

[0006] S2. Determine the coordinates of all endpoints of each straight segment of the combined coil in a rectangular coordinate system. Assume the coil consists of m straight segments, with their vertices being P1, P2, ..., Pn. m , with (xx) i yy i ,zz i () represents the spatial coordinates of the i-th vertex;

[0007] S3, segment calculation each straight line segment in space any point P(x0, y0, z0) generated magnetic field, wherein a current-carrying straight line segment two end points are A and B, the straight line segment AB in P point generated magnetic field intensity is With AB as the axis of rotation, the polar coordinate system is established, at this time all current microelement In P point generated magnetic field intensity microelement The direction of all current microelement The amplitude H l Of:

[0008]

[0009] Wherein, wherein I is the current, l is the integral variable, r is the current element To P point vector length The modulus, θ1, θ2 respectively A(a0, a1, a2), B(b0, b1, b2) two points to P point vector length angle, a is the vertical distance from P point to straight line segment AB, d1, d2, d3 respectively straight line segment AP, BP, AB length;

[0010] S4, determine The direction of all current microelement The direction of all current microelement The direction of all current microelement The same, The coordinates of (b0-a0, b1-a1, b2-a2), The coordinates of (x0-a0, y0-a1, z0-a2), with Respectively represents the unit vector of the coordinate axis x, y, z of the rectangular coordinate system, then:

[0011]

[0012]

[0013] Can be obtained:

[0014] Thus the magnetic field intensity generated by the current-carrying straight line segment AB is:

[0015]

[0016] For the i-th straight line segment, the magnetic field generated at P point in the rectangular coordinate system is:

[0017]

[0018] So the magnetic field generated by the entire combination coil at P point in the rectangular coordinate system is:

[0019]

[0020] S5, set the shielding coefficient considering the magnetic shielding effect of the ferromagnetic material, assuming that the shielding coefficient corresponding to the i-th current-carrying straight line segment is K ti , H xi , H yi , H zi respectively represent the magnetic field components generated by the i-th current-carrying straight line segment at an arbitrary position point P in space, and the magnetic field components generated by the combination coil containing m straight line segments at the point P are:

[0021]

[0022] Take a plane outside the magnetic shielding surface as the measurement plane, the measurement plane and the combination coil are located on the two sides of the magnetic shielding surface, and the magnetic field measurement values of n measurement points on the measurement plane are obtained directly by the arranged magnetic sensor array, wherein the magnetic field measurement value of the j-th measurement point is denoted as H sxj , H syj and H szj , the shielding coefficient K ti corresponding to the i-th current-carrying straight line segment is obtained by using the differential evolution algorithm for optimization x , H' y and H' z .

[0023] In any of the above technical solutions, further, the differential evolution algorithm comprises:

[0024] The shielding coefficient K ti is in the range of 0 ti ≤1, the initial value of the shielding coefficient K ti is set to 1.

[0025] An initialization population with a number of individuals NP is randomly generated, and a scaling factor FA and a crossover probability CR are determined.

[0026] According to the combination coil magnetic field calculation formula in step S5 and the spatial coordinates of the n measurement points on the measurement plane, the magnetic field measurement value of the j-th measurement point on the measurement plane is calculated and denoted as H cxj , H cyj and H czj , the magnetic field measurement values H sxj , H syj and H szj obtained directly by the arranged magnetic sensor array in step S5 are combined, and a target function F reflecting the approximation degree of the calculated values and the measured values of the magnetic fields of the n measurement points on the measurement plane is established:

[0027]

[0028] Calculate the objective function F of each individual in the initial population, judge whether the termination condition is met or the evolution generation g reaches the preset maximum value, if yes, terminate the evolution, and output the best individual as the optimal solution, if not, continue the mutation, crossover and selection operations, obtain a new generation population, at the same time, the evolution generation g = g + 1, and re-perform the forward calculation;

[0029] The shielding coefficient K ti as the optimal shielding coefficient K ti_best And output.

[0030] In any of the technical solutions described above, further, the termination condition is:

[0031]

[0032] That is, the objective function value F is less than or equal to 1‰ of the maximum value of the magnetic field modulus of the n measurement points on the measurement plane 3.

[0033] The beneficial effects of the present application are:

[0034] The technical solution in the present application splits the complex coil into multiple straight line segments, and then combines them to form a combined coil, which is convenient for calculation. As long as the end point coordinates and the current are obtained, the magnetic field generated at any position point in space can be directly obtained through the magnetic field calculation method provided by the present application. Compared with the magnetic field numerical analysis software, the present application does not need to set too many physical parameters, and the process is more simple and the calculation efficiency is higher.

[0035] The present application adds a calculation process considering the magnetic shielding effect of ferromagnetic materials, avoiding the influence of the common ferromagnetic materials around the energized coil in the actual application scene, improving the spatial magnetic field calculation precision, and significantly expanding the application range of the magnetic field calculation method provided by the present application;

[0036] The magnetic field calculation method provided by the present application is not limited to the direct current energization condition, but also applicable to the alternating current energization condition with stable frequency.

[0037] For the same type of energized coil configuration, the shielding coefficient K ti obtained through one magnetic field measurement can be obtained. ti And the shielding coefficient K ti is applicable to the calculation of the magnetic field of the entire space outside the shielding layer.

[0038] In the process of solving the shielding coefficient K tiFurther optimization, while accelerating the convergence process of magnetic field calculation, can greatly improve the accuracy of spatial magnetic field forward calculation, thereby depicting a more detailed magnetic field calculation model and improving the efficiency of spatial magnetic field evaluation. BRIEF DESCRIPTION OF DRAWINGS

[0039] The above and additional aspects of the present application will become apparent and easy to understand from the following description of the embodiments with reference to the accompanying drawings, and the advantages of the present application will be read obviously from the embodiments.

[0040] Figure 1 It is a coil equivalent section diagram of a magnetic shielding effect considering arbitrary shape energized coil magnetic field calculation method according to an embodiment of the present application;

[0041] Figure 2 It is a right-angle coordinate system space arbitrary current-carrying straight line segment magnetic field calculation schematic diagram of a magnetic shielding effect considering arbitrary shape energized coil magnetic field calculation method according to an embodiment of the present application;

[0042] Figure 3 It is a schematic diagram of arranging sensors outside the magnetic shielding surface to measure the energized coil of a magnetic shielding effect considering arbitrary shape energized coil magnetic field calculation method according to an embodiment of the present application;

[0043] Figure 4 It is a differential evolution algorithm flow chart of a magnetic shielding effect considering arbitrary shape energized coil magnetic field calculation method according to an embodiment of the present application.

[0044] Wherein, 1-combination coil, 2-magnetic shielding surface, 3-measurement plane, 4-magnetic sensor array. DETAILED DESCRIPTION

[0045] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the present application will be further described in detail below in combination with the drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0046] In the following description, a lot of specific details are set forth in order to facilitate a thorough understanding of the present application, however, the present application can also be implemented in other ways different from those described herein, therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0047] The embodiment provides a magnetic shielding effect considering arbitrary shape energized coil magnetic field calculation method, which comprises the following steps:

[0048] S1. An arbitrarily shaped energized coil is equivalently divided into a combination coil of multiple straight line segments. The straight line segments of the coil are directly cut off at both ends to form straight line segments. The arc-shaped segments of the coil are divided along the circumference and equivalently transformed into multiple straight line segments. All the processed straight line segments are combined to form an equivalent combination coil.

[0049] Specifically, the energized coil is a single-turn thin wire, and the influence of the wire diameter is ignored; for example... Figure 1 As shown, typical energized coils of circular, rectangular, and irregular shapes are equivalent to straight line segments after being subdivided. Theoretically, the denser the straight line segment units of the energized coil, the smaller the magnetic field calculation error when the arc segments are equivalently replaced by straight line segments, and the higher the accuracy of the spatial magnetic field calculation. However, the computational load will increase. To balance computational efficiency and accuracy, the number of subdivided units of the energized coil should be reasonably determined. Generally, the best overall efficiency of magnetic field calculation is achieved when the arc segment is divided into straight line segments every 11.25° of the arc, which is 1 / 32 of the circumference angle. If the arc segment is divided too densely, the effect on improving the accuracy of the magnetic field calculation is not significant, while if the segment is divided too sparsely, the accuracy of the magnetic field calculation will be significantly reduced.

[0050] S2. Determine the coordinates of all endpoints of each straight segment of the combined coil in a rectangular coordinate system. Assume the coil consists of m straight segments, with their vertices being P1, P2, ..., Pn. m , with (xx) i yy i ,zz i ) represents the spatial coordinates of the i-th vertex.

[0051] The coordinates of the two endpoints of the i-th line segment are:

[0052] Endpoint 1 coordinates: (xx i yy i ,zz i ), coordinates of endpoint 2: (xx i+1 yy i+1 ,zz i+1 ).

[0053] The coordinates of the two endpoints of the m-th straight segment are:

[0054] Endpoint 1 coordinates: (xx m yy m ,zz m The coordinates of endpoint 2 are (xx1, yy1, zz1).

[0055] Specifically, in the conventional approach, after step S2, we can use the Biot-Sava law to obtain:

[0056]

[0057] Where I is the current, l is the integral variable, and r is the current element. The radius vector to point P The modulus.

[0058] The desired magnetic field strength can be obtained using the above formula. However, in a rectangular coordinate system, solving the above integral expression for any current-carrying straight line segment in space is very difficult. Therefore, we consider decomposing any current-carrying straight line segment in space into current-carrying straight line segments that are easy to integrate directly, so that the magnetic field of any current-carrying straight line segment can be expressed as the vector sum of the magnetic fields of these decomposed current-carrying straight line segments.

[0059] like Figure 2 As shown, this invention uses a combination of rectangular and polar coordinate systems to solve this problem, and solves for the magnetic field of the current-carrying straight line segment in the rectangular coordinate system, as follows:

[0060] S3. Calculate the magnetic field generated by each straight line segment at any point P(x0, y0, z0) in space. One current-carrying straight line segment has endpoints A and B, and the magnetic field strength generated by this segment AB at point P is: Establish a polar coordinate system with the line containing AB as the axis of rotation. At this point, all current infinitesimal elements... The infinitesimal magnetic field strength element generated at point P The directions are all along the same direction Therefore, the magnetic field strength is:

[0061]

[0062] It is readily apparent to those skilled in the art that:

[0063]

[0064] Substituting into the integral expression in rectangular coordinates, we get amplitude H l for:

[0065]

[0066] Where θ1 and θ2 are the angles between the radius vectors of points A(a0,a1,a2) and B(b0,b1,b2) and point P, respectively, and a is the perpendicular distance from point P to line segment AB, a = d1sinθ1, d1, d2, and d3 are the lengths of line segments AP, BP, and AB, respectively:

[0067]

[0068] S4, Confirm direction All current elements The directions are all related to the vector Same direction The coordinates of the point A are (b0-a0, b1-a1, b2-a2), The coordinates of the point A are (b0-a0, b1-a1, b2-a2), The coordinates of the point A are (b0-a0, b1-a1, b2-a2),

[0069]

[0070]

[0071] It can be obtained that:

[0072] Thus, the magnetic field strength generated by the current-carrying straight line segment AB can be obtained as:

[0073]

[0074] The magnetic field generated by the i-th straight line segment at point P in the rectangular coordinate system is:

[0075]

[0076] Therefore, the magnetic field generated by the entire combination coil at point P in the rectangular coordinate system is:

[0077]

[0078] For any shaped current-carrying coil, after being equivalently converted into a combination coil, as long as the coordinates of its end points are obtained, the magnetic field generated by the coil at any position in space can be directly obtained by the magnetic field calculation method described in the present application. Compared with magnetic field numerical analysis software, the method does not require excessive physical parameter settings, has a more concise process, and has higher calculation efficiency.

[0079] There are often ferromagnetic materials around the current-carrying coil that affect the spatial magnetic field distribution, resulting in a certain difference between the magnetic field distribution of the current-carrying coil and the magnetic field distribution when the ferromagnetic material is not considered. Therefore, in actual physical scenarios, a shielding coefficient considering the magnetic shielding effect of the ferromagnetic material needs to be added to the above-mentioned current-carrying coil magnetic field calculation to more accurately obtain the spatial magnetic field generated by the current-carrying coil.

[0080] The method for calculating the spatial magnetic field of a current-carrying coil considering the magnetic shielding effect comprises the following steps:

[0081] S5, set a shielding coefficient considering the magnetic shielding effect of the ferromagnetic material, and assume that the shielding coefficient corresponding to the i-th current-carrying straight line segment is K ti . The magnetic field generated by the i-th current-carrying straight line segment at point P in the rectangular coordinate system is: xi yi zi ​​Let represent the components of the magnetic field generated at any point P in space by the i-th current-carrying straight segment when the presence of ferromagnetic material is not considered. Then, considering the presence of ferromagnetic material, the components of the magnetic field generated at point P by the combined coil containing m straight segments need to be supplemented with the corresponding shielding coefficient K. ti The formula for calculating the magnetic field of the combined coil is:

[0082]

[0083] like Figure 3 As shown, a plane outside the magnetic shielding surface 2 is taken as the measurement plane 3. The measurement plane 3 and the combined coil 1 are located on opposite sides of the magnetic shielding surface 2. The magnetic field measurement values ​​of n measurement points on the measurement plane 3 are directly obtained through the arranged magnetic sensor array 4, where the magnetic field measurement value of the j-th measurement point is denoted as H. sxj H syj and H szj The shielding coefficient K corresponding to the i-th current-carrying straight segment is obtained by using the differential evolution algorithm. ti Substituting these values ​​into the above formula for calculating the magnetic field of the combined coil, the magnetic field H' at any point in space surrounding the combined coil 1, considering the magnetic shielding effect of the ferromagnetic material, can be obtained through forward modeling. x H' y and H' z The magnetic field value calculated at this time takes into account the magnetic shielding effect of ferromagnetic materials, and is closer to the real magnetic field value.

[0084] like Figure 4 As shown, the computational process of the differential evolution algorithm includes:

[0085] Due to the shielding effect of ferromagnetic materials, the magnetic field value outside the ferromagnetic material is always no greater than the magnetic field value without the shielding effect of the ferromagnetic material, therefore the shielding coefficient K ti The value range is set to 0. <K ti ≤1, first set the shielding coefficient K ti The initial value is 1.

[0086] Randomly generate an initial population of NP individuals and determine the scaling factor FA and the crossover probability CR.

[0087] Based on the formula for calculating the magnetic field of the combined coil in step S5 and the spatial coordinates of the n measurement points on the measurement plane 3, the magnetic field measurement value of the j-th measurement point on the measurement plane 3 is calculated and denoted as H. cxj H cyj and H czj Combined with the magnetic field measurement value H obtained directly by the arranged magnetic sensor array 4 in step S5, sxj H syj and H szj, a target function F reflecting the approximation degree of the calculated values of the magnetic fields of the n measuring points on the measuring plane 3 and the measured values is established:

[0088]

[0089] The target function F of each individual in the initial population is calculated, and it is determined whether the termination condition is met or the evolution number g reaches the preset maximum value; if yes, the evolution is terminated, and the best individual is output as the optimal solution; if no, the mutation, crossover and selection operations are continued to obtain a new population, the evolution number g is g+1, and the forward calculation is performed again.

[0090] The above steps are repeated until the termination condition of the differential evolution algorithm is met, and the termination condition is set as:

[0091]

[0092] That is, the target function value F is less than or equal to 1‰ of the maximum value of the magnetic field modulus of the n measuring points on the measuring plane 3.

[0093] The shielding coefficient K ti that meets the termination condition is output as the optimal shielding coefficient K ti_best .

[0094] In summary, the application provides a magnetic field calculation method for an arbitrary shape current coil considering magnetic shielding effect, which comprises:

[0095] S1, an arbitrary shape current coil is equivalent to a combination coil composed of multiple straight line segments, wherein the straight line segments of the coil are directly truncated at both ends to form straight line segments, and the arc-shaped segments of the coil are divided along the circumferential direction and equivalent to multiple straight line segments, and all the processed straight line segments are combined to form an equivalent combination coil.

[0096] S2, all end point coordinates of the straight line segments of the combination coil in the rectangular coordinate system are determined, and the coil is composed of m straight line segments, and the vertices are P1, P2, …, P m , and the spatial coordinates of the i-th vertex are represented by (xx i , yy i , zz i ).

[0097] S3, the magnetic field generated by each straight line segment at an arbitrary point P(x0, y0, z0) in space is calculated, wherein the end points of the straight line segment with a current are A and B, and the magnetic field intensity generated by the straight line segment AB at the point P is A polar coordinate system is established with the straight line AB as the rotation axis, and all current elements generate a magnetic field intensity element at the point P, and the directions of the magnetic field intensity elements generated by all current elements the amplitude H of the vector l is:

[0098]

[0099] wherein, wherein I is the current, l is the integral variable, r is the current element the vector length of P point the modulus value, θ1, θ2 are the angles of the vector of points A(a0, a1, a2), B(b0, b1, b2) to P point, a is the perpendicular distance from P point to straight line segment AB, d1, d2, d3 are the lengths of straight line segments AP, BP, AB respectively.

[0100] S4, determine the direction of all current elements the direction of the vector is the same, the coordinates of (b0-a0, b1-a1, b2-a2), the coordinates of (x0-a0, y0-a1, z0-a2), and respectively represent the unit vectors of the coordinate axes x, y, z of the rectangular coordinate system, then:

[0101]

[0102]

[0103] It can be obtained:

[0104] Thus the magnetic field strength generated by the current-carrying straight line segment AB can be obtained:

[0105]

[0106] The components of the magnetic field generated by the i-th straight line segment at point P in the rectangular coordinate system are:

[0107]

[0108] Therefore, the components of the magnetic field generated by the entire combination coil at point P in the rectangular coordinate system are:

[0109]

[0110] S5, set the shielding coefficient considering the magnetic shielding effect of ferromagnetic material, assuming that the shielding coefficient corresponding to the i-th current-carrying straight line segment is K ti . H xi , H yi , H ziLet Bxi, Byi and Bzi respectively represent the magnetic field components generated by the i-th current-carrying straight line segment at an arbitrary position point P in space, then the magnetic field components generated by the combination coil containing m straight line segments at the point P are:

[0111]

[0112] Taking a certain plane outside the magnetic shielding surface as a measurement plane 3, magnetic field measurement values of n measurement points on the measurement plane 3 are obtained through the arranged magnetic sensor array, and are recorded as H sx , H sy and H sz , a shielding coefficient K ti corresponding to the i-th current-carrying straight line segment is obtained by optimization using a differential evolution algorithm, and is substituted into the component formula of the magnetic field intensity to obtain the magnetic field at an arbitrary position point around the combination coil through forward calculation.

[0113] The steps in the application can be adjusted in sequence, combined and reduced according to actual needs.

[0114] Although the application has been disclosed in detail with reference to the drawings, it should be understood that the description is only exemplary and is not intended to limit the application of the application. The scope of protection of the application is defined by the appended claims, and can include various modifications, improvements and equivalent solutions made to the application without departing from the scope and spirit of the application.

Claims

1. A method for calculating a magnetic field of an arbitrary shape energized coil considering a magnetic shielding effect, characterized by, The steps of the method include: S1, equivalently dividing an arbitrary shape energized coil into a combination coil of multiple straight line segments, wherein the straight line segments of the coil are directly truncated at both end positions to divide the straight line segments, and the arc-shaped segments of the coil are divided along the circumferential direction and equivalently converted into multiple straight line segments, and all the processed straight line segments are combined to form an equivalent combination coil; S2. Determine the coordinates of all endpoints of each straight segment of the combined coil in a rectangular coordinate system. Assume the coil consists of m straight segments, with their vertices being P1, P2, ..., Pn. m , with (xx) i yy i ,zz i () represents the spatial coordinates of the i-th vertex; S3, segment calculates each straight line segment in space any point P(x0, y0, z0) generated magnetic field, wherein a current straight line segment two end points are A and B, respectively, the straight line segment AB in P point generated magnetic field intensity is With AB as the axis of rotation, the polar coordinate system is established, at this time all current micro-element In P point generated magnetic field intensity micro-element The direction of all current micro-element The amplitude H l Is: wherein, I is the current, I is the integral variable, r is the current element the vector length to point P the modulus of the vector length to point P, θ1, θ2 are the angles of the vector length of points A(a0, a1, a2), B(b0, b1, b2) to point P, a is the perpendicular distance of point P to straight line segment AB, d1, d2, d3 are the lengths of straight line segments AP, BP, AB, respectively; S4, determine the direction of all the current elements have the same direction as the vector the coordinates of are (b0-a0, b1-a1, b2-a2), the coordinates of are (x0-a0, y0-a1, z0-a2), respectively, representing the unit vectors of the coordinate axes x, y, z of the rectangular coordinate system, then The following can be obtained: Thus, the magnetic field strength generated by the current-carrying straight line segment AB can be obtained as: For the i-th straight line segment, the magnetic field generated at the P point in the rectangular coordinate system has the following components: Therefore, the magnetic field generated at the P point by the entire combination coil in the rectangular coordinate system has the following components: S5, set shielding coefficient considering the magnetic shielding effect of ferromagnetic material, assuming the shielding coefficient corresponding to the i-th current-carrying straight line segment is K ti , H xi , H yi , H zi respectively represent the magnetic field components generated by the i-th current-carrying straight line segment at an arbitrary position point P in space, and the magnetic field components generated by the combination coil containing m straight line segments at the point P are: Taking a certain plane outside the magnetic shielding surface (2) as a measurement plane (3), the measurement plane (3) is located on both sides of the magnetic shielding surface (2) respectively with the combined coil (1), the magnetic field measurement values of n measurement points on the measurement plane (3) are obtained by directly measuring through the arranged magnetic sensor array (4), wherein the magnetic field measurement value of the jth measurement point is denoted as H sxj , syj , szj , the shielding coefficient K ti corresponding to the ith current-carrying straight line segment is obtained by using a differential evolution algorithm for optimization, and the components of the magnetic field intensity are substituted into the formula to obtain the magnetic field at any position around the combined coil (1) through forward calculation, H' x , y , z .

2. The method of claim 1, wherein the method is characterized by, The differential evolution algorithm comprises: Shielding coefficient K ti The value range is 0 < K ti ≤ 1, set shielding coefficient K ti The initial value is 1; An initial population with NP individuals is randomly generated, and a scaling factor FA and a crossover probability CR are determined; According to the formula for calculating the magnetic field of the combined coil in step S5 and the spatial coordinates of the n measuring points on the measuring plane (3), the magnetic field measurement value of the jth measuring point on the measuring plane (3) is calculated and recorded as H cxj , cyj , and H czj , and the magnetic field measurement values H sxj , syj , and H szj , directly measured by the magnetic sensor array (4) arranged in step S5, a target function F reflecting the approximation degree of the calculated and measured magnetic field values of the n measuring points on the measuring plane (3) is established: The objective function F of each individual in the initial population is calculated, and it is judged whether the termination condition is met or the evolution generation g reaches the preset maximum value; if yes, the evolution is terminated, and the best individual is output as the optimal solution; if no, the mutation, crossover and selection operations are continued to obtain a new generation population, the evolution generation g is g+1, and the forward calculation is performed again; The shielding coefficient K satisfying the termination condition is determined ti The optimal shielding coefficient K is determined ti_best and output.

3. The method of claim 2, wherein the magnetic shielding effect is considered. The termination condition is: That is, the objective function value F is less than or equal to 1‰ of the maximum value of the magnetic field modulus of the n measurement points on the measurement plane (3).

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